Substrate gripping apparatus

ABSTRACT

The present invention relates to a substrate gripping apparatus includes a base, a plurality of support posts which are vertically movable relative to the base, a lifting mechanism configured to lift the support posts, and a substrate holder and a substrate guide member mounted to each of the support posts. Each of the support posts includes a relative movement mechanism configured to move the substrate holder in such a direction that the substrate holder releases a peripheral portion of a substrate, while raising the substrate guide member relative to the substrate holder, when the support post moves upward, and to move the substrate holder in such a direction that the substrate holder grips the peripheral portion of the substrate, while lowering the substrate guide member relative to the substrate holder, when the support post moves downward.

CROSS REFERENCE TO RELATED APPLICATION

This document claims priority to Japanese Patent Application No.2013-3291 filed Jan. 11, 2013, the entire contents of which are herebyincorporated by reference.

BACKGROUND OF THE INVENTION

1. Field of the Invention

The present invention relates to a substrate gripping apparatus, andmore particularly to a substrate gripping apparatus which can be used ina cleaning apparatus or a drying apparatus for a substrate, such as asemiconductor wafer.

2. Description of the Related Art

In a semiconductor device fabrication process, a substrate is subjectedto a cleaning process or a drying process after the substrate ispolished or plated. For example, in cleaning of a substrate, a cleaningliquid is supplied to the substrate while the substrate, which isgripped by a substrate gripping apparatus, is being rotated. A mechanismof gripping a substrate by chucks, which are driven by an actuator, isknown as a conventional substrate gripping apparatus.

SUMMARY OF THE INVENTION

The present invention is directed to an improvement of the conventionalsubstrate gripping apparatus, and provides a substrate grippingapparatus which can securely grip a substrate.

An embodiment is a substrate gripping apparatus, comprising: a base; aplurality of support posts which are supported by the base and arevertically movable relative to the base; a lifting mechanism configuredto lift the support posts; and a substrate holder and a substrate guidemember mounted to each of the support posts. Each of the support postsincludes a relative movement mechanism configured to move the substrateholder and the substrate guide member relative to each other. Therelative movement mechanism is configured to move the substrate holderin such a direction that the substrate holder releases a peripheralportion of a substrate, while raising the substrate guide memberrelative to the substrate holder, when the support post moves upward,and to move the substrate holder in such a direction that the substrateholder grips the peripheral portion of the substrate, while lowering thesubstrate guide member relative to the substrate holder, when thesupport post moves downward.

The relative movement mechanism includes: a first rod; a second rodconfigured to be vertically movable relative to the first rod and to belifted by the lifting mechanism; a first spring arranged between thebase and the first rod and configured to bias the first rod downward; asecond spring arranged between the first rod and the second rod andconfigured to bias the second rod downward; a support shaft secured tothe first rod and configured to rotatably support the substrate holder;and a coupling mechanism configured to couple the second rod to thesubstrate holder.

The first spring has a spring constant which is lower than a springconstant of the second spring.

The first spring has a spring constant which is higher than a springconstant of the second spring.

The substrate guide member is secured to the second rod.

The relative movement mechanism is configured to raise the substrateguide member to a position higher than the substrate holder and lowerthe substrate guide member to a position lower than the substrateholder.

The substrate holders are arranged at equal intervals around a centralaxis of the base and are configured to perform centering of thesubstrate by gripping the peripheral portion of the substrate.

The substrate holder has a chuck portion configured to grip theperipheral portion of the substrate and a slope on which the peripheralportion of the substrate is to be placed, and the chuck portion isformed integrally on the slope.

When the support posts move upward, the substrate guide members areraised relative to the substrate holders. Therefore, the substrate,which has been transported from a transport mechanism, is guided by thesubstrate guide members to the substrate holders, so that the substrateholders can securely grip the substrate. When the support posts movedownward and the substrate holders grip the substrate, the substrateguide members are lowered relative to the substrate holders. This canprevent a liquid from bouncing off the substrate guide members when thesubstrate gripping apparatus is applied to an apparatus which uses theliquid, such as a substrate cleaning apparatus.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a vertical cross-sectional view of a substrate grippingapparatus according to a first embodiment;

FIG. 2 is a plan view of the substrate gripping apparatus according tothe first embodiment;

FIG. 3 is a diagram corresponding to FIG. 1, showing the substrategripping apparatus when a lifting mechanism is in a raised position;

FIG. 4 is an enlarged view of a support post and a substrate holder;

FIG. 5A is a top view of the support post and the substrate holder;

FIG. 5B is a cross-sectional view of the support post and the substrateholder as viewed in a direction indicated by arrow A shown in FIG. 4;

FIG. 6 is a diagram corresponding to FIG. 4, showing the substrategripping apparatus when the support post is lifted by the liftingmechanism;

FIG. 7A is a diagram showing the substrate holder when the support postis in a raised position;

FIG. 7B is a diagram showing the substrate holder when the support postis in a lowered position;

FIG. 8A is a diagram showing the substrate holder and a substrate guidemember when the support post is in the lowered position;

FIG. 8B is a diagram showing the substrate holder and the substrateguide member when the support post is in the raised position;

FIG. 9 is a diagram showing a substrate gripping apparatus according toa second embodiment; and

FIG. 10 is a diagram showing the substrate gripping apparatus of FIG. 9when the support post is lifted by the lifting mechanism.

DETAILED DESCRIPTION

Embodiments will now be described in detail with reference to thedrawings.

FIG. 1 is a vertical cross-sectional view of a substrate grippingapparatus according to a first embodiment. FIG. 2 is a plan view of thesubstrate gripping apparatus according to the first embodiment.

As shown in FIG. 1 and FIG. 2, the substrate gripping apparatus includesa base 1 having four arms 1 a, four support posts 2 each supported by adistal end of each arm 1 a, and four substrate holders 3 coupled to thesupport posts 2, respectively. The base 1 is secured to an upper end ofa rotational shaft 5, which is rotatably supported by bearings 6. Thebearings 6 are fixed to an inner circumferential surface of acylindrical member 7 that surrounds the rotational shaft 5. A lower endof the cylindrical member 7 is mounted to a pedestal 9 and is fixed inits position. The rotational shaft 5 is coupled to a motor 15 throughpulleys 11, 12 and a belt 14 so that the base 1 is rotated about itsaxis when the motor 15 is set in motion. A symbol W represents asubstrate, such as a wafer. A wafer W is gripped by the substrateholders 3 and rotated about its central axis by the motor 15.

A lifting mechanism 20 for lifting the support posts 2 is provided so asto surround the cylindrical member 7. The lifting mechanism 20 isconfigured to be able to slide vertically relative to the cylindricalmember 7. The lifting mechanism 20 has four pushers 20 a that contactlower ends of the four support posts 2 to lift the support posts 2. Afirst gas chamber 21 and a second gas chamber 22 are formed between anouter circumferential surface of the cylindrical member 7 and an innercircumferential surface of the lifting mechanism 20. The first gaschamber 21 and the second gas chamber 22 communicate with a first gasflow passage 24 and a second gas flow passage 25, respectively. Thefirst gas flow passage 24 and the second gas flow passage 25 are coupledto a not-shown pressurized gas supply source. When pressure in the firstgas chamber 21 is increased higher than pressure in the second gaschamber 22, the lifting mechanism 20 is moved upward as shown in FIG. 3.Conversely, when the pressure in the second gas chamber 22 is increasedhigher than the pressure in the first gas chamber 21, the liftingmechanism 20 is moved downward as shown in FIG. 1. In this manner, thelifting mechanism 20 can move up and down the four support posts 2simultaneously.

The outer circumferential surfaces of the four support posts 2 aresecured to a ring member 31 so that the support posts 2 can movevertically together with the ring member 31. The ring member 31 extendsalong an arrangement direction of the support posts 2 and is locatedbelow the base 1. The ring member 31, the rotational shaft 5, the base1, and the cylindrical member 7 are arranged concentrically.

A rotary cup 28 is secured to an upper surface of the base 1. Thisrotary cup 28 is provided for the purposed of receiving a liquid thathas been scattered around by a centrifugal force from the rotating waferW. FIG. 1 and FIG. 3 show a vertical cross-sectional view of the rotarycup 28. The rotary cup 28 is arranged so as to surround the peripheralportion of the wafer W in its entirety. The rotary cup 28 has a verticalcross-sectional shape that is inclined radially inwardly. Further, therotary cup 28 has an inner circumferential surface that is formed by asmooth curved surface. An upper end rim of the rotary cup 28 lies closeto the wafer W, and an inner diameter of the rotary cup 28, at its upperend, is slightly larger than a diameter of the wafer W. Cutout portions28 a, each having a shape conforming to the shape of the outer peripheryof each support post 2, are formed in positions corresponding topositions of the support posts 2. Obliquely extending drain holes (notshown) are formed in the bottom of the rotary cup 28.

The four support posts 2 have the same construction, and the foursubstrate holders 3 have the same construction. FIG. 4 is an enlargedview of the support post 2 and the substrate holder 3. FIG. 5A is a topview of the support post 2 and the substrate holder 3, and FIG. 5B is across-sectional view of the support post 2 and the substrate holder 3 asviewed in a direction indicated by arrow A shown in FIG. 4. The arm 1 aof the base 1 has a holding member 1 b for slidably holding the supportpost 2. The holding member 1 b may be formed integrally with the arm 1a. The holding member 1 b has a vertical through-hole through which thesupport post 2 is inserted. The diameter of the through-hole is slightlylarger than the diameter of the support post 2, so that the support post2 can move vertically relative to the base 1.

The substrate holder 3 has a slope 3 b which is an upper surfacethereof. This slope 3 b is inclined downward in a radially inwarddirection of the wafer W. A chuck potion 3 a, which is brought intocontact with the peripheral portion of the wafer W, is formed integrallyon the slope 3 b of the substrate holder 3. In this embodiment, the foursubstrate holders 3 are provided for gripping the peripheral portion ofthe wafer W as shown in FIG. 2. The peripheral portion of the wafer W isfirst placed on the slopes 3 b, and is then gripped by the chuckportions 3 a. The substrate holders 3 are arranged at equal intervalsaround the central axes of the base 1 and the rotational shaft 5.Accordingly, centering of the wafer W can be performed automaticallywhen the substrate holders 3 grip the peripheral portion of the wafer W.

Each of the support posts 4 includes a first rod 35, which is verticallyslidably held by the holding member 1 b, and a second rod 36 housed inthe first rod 35. The substrate holder 3 is coupled to upper ends of thefirst rod 35 and the second rod 36. The first rod 35 has a cylindricalshape, and the second rod 36 is vertically movable in the first rod 35.Thus, the second rod 36 can move vertically relative to the first rod35. The first rod 35 is secured to the ring member 31.

A first spring 41 is disposed between the base 1 and the first rod 35.More specifically, a spring stopper 44 is secured to the outer peripheryof the first rod 35, and the first spring 41 is arranged between thespring stopper 44 and the holding member 1 b of the base 1. The firstspring 41 biases the first rod 35 downward.

A second spring 42 is disposed between the first rod 35 and the secondrod 36. More specifically, a spring stopper 45 is secured to the outerperiphery of the second rod 36, and the second spring 42 is arrangedbetween the spring stopper 45 and the lower end of the first rod 35. Thesecond spring 42 biases the second rod 36 downward. The first spring 41has a spring constant which is lower than a spring constant of thesecond spring 42.

When the pusher 20 a of the lifting mechanism 20 pushes up the secondrod 36, an upward force is applied from the second spring 42 to thefirst rod 35, whereby the first rod 35 and the second rod 36 move upwardtogether against a reaction force of the first spring 41. As shown inFIG. 6, the upward movement of the first rod 35 is stopped when the ringmember 31 contacts the lower surface of the base 1, while the second rod36 continues to move upward. The upward movement of the second rod 36 isstopped when the second rod 36 reaches a predetermined height. In thismanner, the upward movement of the second rod 36 is stopped after theupward movement of the first rod 35 is stopped. Instead of the ringmember 31, a stopper, which is brought into contact with the lowersurface of the base 1, may be provided on each support post 2. Also inthis case, the upward movement of the second rod 36 can be stopped afterthe upward movement of the first rod 35 is stopped.

The substrate holder 3 is rotatably supported by a support shaft 46secured to the first rod 35. A pin 47 is secured to a lower portion ofthe substrate holder 3, and is inserted into an elongated hole 48 formedin the upper end of the second rod 36. Thus, the substrate holder 3 iscoupled to the second rod 36 through engagement between the pin 47 andthe elongated hole 48. The pin 47 and the elongated hole 48 constitute acoupling mechanism for coupling the substrate holder 3 to the second rod36. As described above, the second rod 36 moves upward slightly relativeto the first rod 35 after the upward movement of the first rod 35 isstopped. When the second rod 36 moves upward relative to the first rod35, the second rod 36 pushes up the pin 47, which is secured to thesubstrate holder 3, to thereby rotate the substrate holder 3 slightlyabout the support shaft 46.

FIG. 7A is a diagram showing the substrate holder 3 when the supportpost 2 is in a raised position, and FIG. 7B is a diagram showing thesubstrate holder 3 when the support post 2 is in a lowered position. Asshown in FIG. 7A, when the substrate holder 3 is slightly rotated aboutthe support shaft 46 with the upward movement of the support post 2, thechuck potion 3 a is separated from the peripheral portion of the waferW. Thus, the wafer W is released from the substrate holder 3. In thismanner, by simply moving the support post 2 upward, the substrate holder3 can be moved (or rotated) in a direction in which the chuck portion 3a moves away from the peripheral portion of the wafer W to therebyrelease the wafer W. The wafer W that has been released from the chuckportion 3 a stays on the slope 3 b of the substrate holder 3. In thisstate, the wafer W is carried out of the substrate holder 3 by anot-shown transporting mechanism. When another wafer is carried in, thiswafer is placed on the slope 3 b with the support post 2 in the raisedposition.

Operation of gripping the wafer W is performed as follows. When thepusher 20 a is lowered with the wafer W placed on the slope 3 b, thesupport post 2 and the substrate holder 3 are lowered by the reactionforces of the first spring 41 and the second spring 42. When the supportpost 2 is lowered, the second rod 36 is started to be lowered before thefirst rod 35 is started to be lowered. Therefore, as shown in FIG. 7B,the substrate holder 3, which is coupled to the second rod 36, isrotated about the support shaft 46 in a direction in which the chuckportion 3 a moves closer to the peripheral portion of the wafer W untilthe chuck portion 3 a comes into contact with the peripheral portion ofthe wafer W, so that the wafer W is gripped by the substrate holder 3.

The four substrate holders 3 operate simultaneously to grip theperipheral portion of the wafer W. When the chuck portions 3 a of thefour substrate holders 3 grip the peripheral portion of the wafer W,centering of the wafer W is completed at the same time. In this manner,by simply lowering the support posts 2, the substrate holders 3 is moved(or rotated) in the direction in which the chuck portions 3 a movecloser to the peripheral portion of the wafer W, thereby gripping thewafer W with the chuck portions 3 a and simultaneously performingcentering of the wafer W. The ring member 31 is provided mainly for thepurpose of lowering the four support posts 2 in synchronization. Forinstance, even if some of the four support posts 4 cannot movevertically in a smooth manner for some reason, the four support posts 4held by the ring member 31 can be lowered in synchronization.

As shown in FIG. 5B, a substrate guide member 50 for guiding the waferW, which has been transported from a transport device, to the substrateholder 3 is fixed to the upper end of each second rod 36 by screws 51.The substrate guide member 50 is moved vertically together with thesecond rod 36. Therefore, the substrate guide member 50 is movedvertically relative to the first rod 35. More specifically, when thesupport post 2 is raised, the substrate holder 3 is rotated in thedirection in which the chuck portion 3 a moves away from the peripheralportion of the wafer W and, in synchronization with this movement, thesubstrate guide member 50 is moved upward relative to the substrateholder 3 until an upper end of the substrate guide member 50 projectsupward from the substrate holder 3 as shown in FIG. 7A. The substrateguide member 50 has, at its upper end, a tapered surface 50 a forguiding the peripheral portion of the wafer W to the slope (uppersurface) 3 b of the substrate holder 3. As the substrate guide member 50is raised relative to the substrate holder 3, the tapered surface 50 ais moved to a position above the slope 3 b. Therefore, the peripheralportion of the wafer W is guided by the tapered surface 50 a to theslope 3 b of the substrate holder 3.

When the support post 2 is lowered, the second rod 36 is started to movedownward before the first rod 35 is started to move downward. Therefore,the pin 47 in engagement with the elongated hole 48 is lowered togetherwith the second rod 36. As a result, the substrate holder 3 is rotatedabout the support shaft 46 in the direction in which the chuck portion 3a moves closer to the peripheral portion of the wafer W. Insynchronization with the rotation of the substrate holder 3, thesubstrate guide member 50 is lowered relative to the substrate holder 3until the upper end of the substrate guide member 50 lies lower than thesubstrate holder 3 as shown in FIG. 7B. In this manner, when the wafer Wis held by the substrate holders 3, the substrate guide members 50 arelower than the substrate holders 3. This arrangement enables a liquid,which has been supplied to the upper surface of the rotating wafer W, tobe discharged from the peripheral portion of the wafer W by thecentrifugal force without being disturbed by the substrate guide members50. For example, in a case where the substrate gripping apparatus ofthis embodiment is applied to a wafer (substrate) cleaning apparatus, acleaning liquid is supplied onto the upper surface of the wafer W thatis being rotated by the motor 15. This cleaning liquid is forced out ofthe peripheral portion of the wafer W by the centrifugal force. If thesubstrate guide members 50 project upward from the substrate holders 3,the cleaning liquid can bounce off the substrate guide members 50 backonto the upper surface of the wafer W. The substrate gripping apparatusof this embodiment can avoid such bouncing of liquid.

FIG. 8A is a diagram showing the substrate holder 3 and the substrateguide member 50 when the support post 2 is in the lowered position, andFIG. 8B is a diagram showing the substrate holder 3 and the substrateguide member 50 when the support post 2 is in the raised position. Asshown in FIG. 8A, when the support post 2 is in the lowered position,the tapered surface 50 a of the substrate guide member 50 lies outwardlyof the slope 3 b of the substrate holder 3. As shown in FIG. 8B, whenthe support post 2 is in the raised position, the tapered surface 50 aof the substrate guide member 50 lies just above the slope 3 b of thesubstrate holder 3. Accordingly, the wafer W from a transport device isonce received on the tapered surface 50 a of the substrate guide member50, guided downward along the tapered surface 50 a, and then placed onthe slope 3 b of the substrate holder 3. The substrate holders 3 canthus securely grip the wafer W.

FIG. 9 is a diagram showing the substrate gripping apparatus accordingto a second embodiment. With reference to the construction and theoperation of this embodiment which are the same as those of theabove-described first embodiment, a duplicate description thereof willbe omitted. In this embodiment, the first spring 41 has a springconstant which is higher than a spring constant of the second spring 42.Therefore, when the pusher 20 a of the lifting mechanism 20 lifts thesupport post 2, the second rod 36 is firstly started to be raised, andsubsequently the first rod 35 is started to be raised.

FIG. 10 is a diagram showing the substrate gripping apparatus when thesupport post 2 is raised by the lifting mechanism 20. A loadtransmission member 54, which contacts the pusher 20 a, is secured tothe lower end of the first rod 35. This load transmission member 54extends downward through the stopper 45 of the second rod 36. When thesecond spring 42 is compressed, the pusher 20 a comes into contact withthe load transmission member 54 and raises the first rod 35 togetherwith the second rod 36. It is noted that the present invention is notlimited to the illustrated embodiment. For example, the substrategripping apparatus may be configured such that a part of the springstopper 45 comes into contact with the lower end of the first rod 35.The ring member 31 is not provided in this embodiment.

In the above-described first embodiment, immediately before the supportposts 2 stop their upward movement, the substrate holders 3 are rotated(or moved) in such a direction as to release the peripheral portion ofthe wafer W, while in the second embodiment the substrate holders 3 arerotated (or moved) in such a direction as to release the peripheralportion of the wafer W when the upward movement of the support posts 2is started. Therefore, in the second embodiment, the wafer W movesupward together with the support posts 2 with the chuck portions 3 a ofthe substrate holders 3 separated from the peripheral portion of thewafer W. The substrate guide members 50 operate in the same manner as inthe first embodiment. Thus, each substrate guide member 50 movesvertically relative to the substrate holder 3 in synchronization withthe movement (rotation) of the substrate holder 3.

While the present invention has been described with reference to theembodiments, it is understood that the present invention is not limitedto the embodiments described above, but is capable of various changesand modifications within the scope of the inventive concept as expressedherein.

What is claimed is:
 1. A substrate gripping apparatus, comprising: abase; a plurality of support posts which are supported by the base andare vertically movable relative to the base; a lifting mechanismconfigured to lift the support posts; and a substrate holder and asubstrate guide member mounted to each of the support posts, each of thesupport posts including a relative movement mechanism configured to movethe substrate holder and the substrate guide member relative to eachother, the relative movement mechanism being configured to move thesubstrate holder in such a direction that the substrate holder releasesa peripheral portion of a substrate, while raising the substrate guidemember relative to the substrate holder, when the support post movesupward, and to move the substrate holder in such a direction that thesubstrate holder grips the peripheral portion of the substrate, whilelowering the substrate guide member relative to the substrate holder,when the support post moves downward.
 2. The substrate grippingapparatus according to claim 1, wherein the relative movement mechanismincludes: a first rod; a second rod configured to be vertically movablerelative to the first rod and to be lifted by the lifting mechanism; afirst spring arranged between the base and the first rod and configuredto bias the first rod downward; a second spring arranged between thefirst rod and the second rod and configured to bias the second roddownward; a support shaft secured to the first rod and configured torotatably support the substrate holder; and a coupling mechanismconfigured to couple the second rod to the substrate holder.
 3. Thesubstrate gripping apparatus according to claim 2, wherein the firstspring has a spring constant which is lower than a spring constant ofthe second spring.
 4. The substrate gripping apparatus according toclaim 2, wherein the first spring has a spring constant which is higherthan a spring constant of the second spring.
 5. The substrate grippingapparatus according to claim 2, wherein the substrate guide member issecured to the second rod.
 6. The substrate gripping apparatus accordingto claim 1, wherein the relative movement mechanism is configured toraise the substrate guide member to a position higher than the substrateholder and lower the substrate guide member to a position lower than thesubstrate holder.
 7. The substrate gripping apparatus according to claim1, wherein the substrate holders are arranged at equal intervals arounda central axis of the base and are configured to perform centering ofthe substrate by gripping the peripheral portion of the substrate. 8.The substrate gripping apparatus according to claim 1, wherein: thesubstrate holder has a chuck portion configured to grip the peripheralportion of the substrate and a slope on which the peripheral portion ofthe substrate is to be placed; and the chuck portion is formedintegrally on the slope.
 9. A substrate gripping apparatus, comprising:a base; a plurality of support posts which are supported by the base andare vertically movable between a raised position and a lowered positionrelative to the base; a substrate holder mounted to each of the supportposts and to move according to a vertical motion of the support posts togrip a peripheral portion of the substrate when the support posts are inthe lowered position and to release the peripheral portion of thesubstrate when the support posts are in the raised position; and asubstrate guide member mounted to each of the support posts and to moveaccording to the vertical motion of the support posts to support theperipheral portion of the substrate when the support posts are in theraised position, the substrate guide member being lower than thesubstrate holder when the support posts are in the lowered position.